Young Folks' Library, Volume XI (of 20) eBook

which are ascribed to ancient earth-throes without
imagining for a while that the power of modern earthquakes
is altogether less. But when we consider fairly
the share which time had in those ancient processes
of change, when we see that while mountain ranges
were being upheaved or valleys depressed to their present
position, race after race, and type after type appeared
on the earth, and lived out the long lives which belong
to races and to types, we are recalled to the remembrance
of the great work which the earth’s subterranean
forces are still engaged upon. Even now continents
are being slowly depressed or upheaved; even now mountain
ranges are being raised to a new level, tablelands
are in process of formation, and great valleys are
being gradually scooped out. It may need an occasional
outburst, such as the earthquake of August, 1868, to
remind us that great forces are at work beneath the
earth’s surface. But, in reality, the signs
of change have long been noted. Old shore-lines
shift their place, old soundings vary; the sea advances
in one place and retires in another; on every side
Nature’s plastic hand is at work modelling and
remodelling the earth, in order that it may always
be a fit abode for those who are to dwell upon it.

[Illustration]

THE PHOSPHORESCENT SEA

(FROM STUDIES OF ANIMATED NATURE.)

BY W.S. DALLAS.

[Illustration]

It is not merely on land that this phenomenon of phosphorescence
is to be seen in living forms. Among marine animals,
indeed, it is a phenomenon much more general, much
more splendid, and, we may add, much more familiar
to those who live on our coasts. There must be
many in the British Isles who have never had the opportunity
of seeing the light of the glow-worm, but there can
be few of those who have frequented in summer any
part of our coasts, who have never seen that beautiful
greenish light which is then so often visible, especially
on our southern shores, when the water is disturbed
by the blade of an oar or the prow of a boat or ship.
In some cases, even on our own shores, the phenomenon
is much more brilliant, every rippling wave being
crested with a line of the same peculiar light, and
in warmer seas exhibitions of this kind are much more
common. It is now known that this light is due
to a minute living form, to which we will afterward
return.

But before going on to speak in some detail of the
organisms to which the phosphorescence of the sea
is due, it will be as well to mention that the kind
of phosphorescence just spoken of is only one mode
in which the phenomenon is exhibited on the ocean.
Though sometimes the light is shown in continuous
lines whenever the surface is disturbed, at other
times, and, according to M. de Quatrefages, more commonly,
the light appears only in minute sparks, which, however
numerous, never coalesce. “In the little
channel known as the Sund de Chausez,” he writes,
“I have seen on a dark night each stroke of the
oar kindle, as it were, myriads of stars, and the
wake of the craft appeared in a manner besprinkled
with diamonds.” When such is the case the
phosphorescence is due to various minute animals, especially
crustaceans; that is, creatures which, microscopically
small as they are, are yet constructed more or less
on the type of the lobster or cray-fish.